SEOUL, South Korea -- In another sign of warming relations between two wartime foes, a senior North Korean nuclear negotiator will attend a security conference in the United States, a U.S. official confirmed yesterday.

Word of Ri Yong Ho's visit to the forum held by Syracuse University comes on the heels of a breakthrough agreement that will provide much-needed U.S. food aid to North Korea in exchange for a rollback of its nuclear programs.

The agreement announced Wednesday sets in motion a plan laid out by North Korean leader Kim Jong Il before his death in December: to improve relations with the United States and to get back to six-nation disarmament-for-aid negotiations. Significant challenges remain, however, in achieving the long-term goal of the United States and other nations: to persuade Pyongyang to end its nuclear ambitions altogether.

First, diplomats need to iron out the tricky logistics of distributing, and monitoring, the 240,000 metric tons of U.S. food aid earmarked for hungry North Korean children. They also need to work out a timeline for the return of UN nuclear inspectors tasked with verifying whether Pyongyang sticks to its promises.

And while the deal paves the way for unprecedented exchanges with the United States, North Korea still must confront the complicated matter of improving relations with South Korea, still smarting from two deadly incidents in 2010 that Seoul blames on Pyongyang.

The commander of U.S. forces in the Pacific, Adm. Robert Willard, said yesterday he is hopeful but not optimistic about the latest efforts to get North Korea to end its nuclear weapons program.

"In the past we have not seen much change," Willard told a congressional hearing in Washington.

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